"I wasn't a bad soccer player when I was a kid in Baltimore," Lionel Chaiken was saying this week to a visitor. "I played three years of high school ball. But these kids passed me when they were in the seventh grade."

The gestured toward a group of about 15 teen-agers running through drills on the artificial turf of Georgetown University's Kehoe Field, where Gary Darrell, the ex-Diplomat midfielder, was leading them through ball-control exercises.

Watching them briefly, Chaiken resumed, "But we knew when they were 9 and 10 they were going to be good."

Formed in the spring of 1974 from the best young players in the nascent Montgomery Soccer League, the Potomac Kickers team seldom since has contradicted the initial assessment of Chaiken, the assistant coach, and Joe Baer, the head coach. It has won several major youth tournaments in the United States and in Canada, and is competing this weekend in Omaha in the most prestigous one in North America, the McGuire Cup, symbolic of the U.S. championship for 19-and-under teams. The Kickers play St. LOUIS IN THE FIRST ROUND TODAY AT 5:30 P.M. (EDT).

The talent of his team notwithstanding -- nearly every player on the team is an all-Met or all-state player -- Baer admitted winning the Eastern Region championship of the McGuire Cup was somewhat of a surprise. The major obstacle was the schedule: six tournament games in nine days in late May and early June. Four were played within 72 hours.

Asked by Baer three years ago to give his professional expertise to the developing players, Darrell has helped them refine and polish their skills. Their play in the regional tournament, played in the rain at Fairfax's Robinson High School three weeks ago, convinced the former Dip that the Kickers had come of age.